Amy DeStefano was a single mother juggling family life and a full-time job three winters ago when she caught what at first was just a persistent February cold. Then it spiraled into pneumonia and spread to her heart.

By last January, DeStefano, at 39, was on the waiting list for a heart transplant at Massachusetts General Hospital.

Her wait ended late last month when the social worker from Portsmouth, N.H., became the first patient in New England to receive an experimental “beating heart’’ transplant.

TransMedics

A new device circulates blood through a donor’s heart and keeps it beating in a transparent plastic case after removal.

Cardiac transplant surgeons have high hopes for the technology, which is approved in Europe, believing it could improve survival rates for recipients because the donor hearts will be in better condition.

Get Fast Forward in your inbox:

Forget yesterday's news. Get what you need today in this early-morning email.

Typically, after surgeons remove the heart from a donor, they replace the blood with a salt-water solution and place the organ on ice in a chest resembling a picnic cooler. Racing the clock, surgeons have only about four hours to transport the heart and stitch it into the recipient before it becomes too damaged to transplant.

DeStefano is part of a clinical trial testing a machine that circulates blood in the donor’s heart, and keeps it beating in a transparent plastic case after removal. A computerized control system monitors the heart’s metabolism, blood pressure, and electrical state. More than 40 patients in the United States have participated in the trial so far.

Eventually, doctors speculate, the device, made by an Andover company, will keep hearts in good condition longer than four hours, meaning that they could be transported farther and that more donor hearts could be used. Now, about half of hearts from potential donors go unused, either because the donor is too far from a matching recipient or because of abnormalities in the heart.

“The moment we take that heart out of the donor’s body it is deteriorating,’’ said Dr. Bruce Rosengard, who is surgical director of cardiac transplantation at the hospital and who performed DeStefano’s transplant. “We hope to dramatically increase the number of transplants.’’

Yesterday, DeStefano, now 40, sat in a chair in her room at Mass. General, sipping water while nurses took vital signs and blood samples. She walks the floor and does leg-lifts for exercise and said she feels more energetic every day. A recent echocardiogram “shows excellent function,’’ similar to what one would see in an athlete, said Rosengard.

DeStefano said she did not have any reservations about participating in the trial and found the technology fascinating. “It made so much sense,’’ she said.

Patients who receive beating heart transplants face no known special risks, other than the danger of infection, rejection, and other problems that all transplant patients are subject to, Rosengard said. He said he has no financial relationship with the maker of the technology, TransMedics Inc.

About 2,000 patients receive heart transplants in the United States each year, but about 400 people die while waiting for a transplant.

The clinical trial, the largest randomized heart transplant trial ever in the United States, is designed to enroll 128 patients, and company executives expect the study will be completed by the end of the year.

They then plan to apply for approval from the US Food and Drug Administration to market the device, which looks like a rolling cart and can fit on an airplane.

In the trial, doctors are measuring whether patients who receive beating heart transplants have better 30-day survival rates than those who receive traditional transplants and whether the former group has fewer rejection episodes and serious complications, as well as shorter stays in the intensive care unit.

Typically, 92 to 95 percent of heart transplant patients are alive and their new heart is working after 30 days, Rosengard said. The survival rate after five years is about 70 percent, he said.

Dr. Tamer Khayal, vice president of clinical development at TransMedics, said results from clinical trials in Europe, which concluded four years ago, showed 30-day survival rates for patients who received beating heart transplants were almost 98 percent.

European surgeons have successfully transplanted hearts that have been sustained on the device for more than eight hours, he said. Mass. General doctors could travel to Los Angeles and get a heart to transplant into a patient back in Boston, Khayal said. “That’s inconceivable today.’’

Still, prior efforts to build beating-heart technology have ended in failure. And if the technology progresses to attempts to revive damaged organs, that will raise a whole set of new questions about how far doctors can safely push the use of subpar hearts.

When the virus infected DeStefano’s heart, she became dizzy and exhausted and had difficulty breathing. The symptoms grew so bad that she left her job in summer 2009.

By the time she was admitted to Mass. General late last year, she was unable to drive her 11-year-old son and her 9-year-old daughter to school or to shop for groceries.

At first, she was apprehensive about the operation, but eventually accepted that “I needed this.’’

“My quality of life was not what it should be,’’ she said.

Rosengard hopes she will be able to return home next week.

DeStefano said she looks forward to complaining about long days at work again and to family barbecues and beach days swimming with her children.

When the anesthesia first wore off, DeStefano said she was disconcerted by the noticeable thumping in her chest, but she is gladly growing accustomed to it.

BostonGlobe.com complimentary digital access has been provided to you, without a subscription, for free starting today and ending in 14 days. After the free trial period, your free BostonGlobe.com digital access will stop immediately unless you sign up for BostonGlobe.com digital subscription. Current print and digital subscribers are not eligible for the free trial.

Thanks & Welcome to Globe.com

You now have unlimited access for the next two weeks.

BostonGlobe.com complimentary digital access has been provided to you, without a subscription, for free starting today and ending in 14 days. After the free trial period, your free BostonGlobe.com digital access will stop immediately unless you sign up for BostonGlobe.com digital subscription. Current print and digital subscribers are not eligible for the free trial.